code: def speed_direction(bbox1, bbox2):
      cx1, cy1 = (bbox1[0] + bbox1[2]) / 2.0, (
          bbox1[1] + bbox1[3]
      ) / 2.0
      cx2, cy2 = (bbox2[0] + bbox2[2]) / 2.0, (
          bbox2[1] + bbox2[3]
      ) / 2.0
      speed = np.array([cy2 - cy1, cx2 - cx1])
      norm = np.sqrt((cy2 - cy1) ** 2 + (cx2 - cx1) ** 2) + 1e-6
      return speed / norm
  
file_path: PaddleDetection/deploy/pptracking/python/mot/tracker/ocsort_tracker.py
imports: import time
  import numpy
  from ..matching.ocsort_matching import associate, linear_assignment, iou_batch, associate_only_iou
  from ..motion.ocsort_kalman_filter import OCSORTKalmanFilter
label_desc: Use image node_id 4 for calling a global function with example usage: speed_direction(bbox1, bbox2) and returns: unknown